In an automotive passive entry system that includes one or more remote transceiver fobs, it may be desirable to maintain a high level of security while maintaining the lowest latency of actuation. To achieve these requirements, in part, it may be necessary to know if an authorizing fob is inside or outside of a vehicle before actuating passive functions.
A series of one or more short range antennas may be provided inside and outside of the vehicle for use in determining fob locations. The antennas may be activated sequentially to transmit a series of encoded signals to any nearby fobs, which the fobs then respond to via an onboard transmitter to the controlling system located within the vehicle. The responses from the fobs carry signal level information that was acquired during the activation of the antennas. The signal levels reported may then be used, in part, by the passive entry controlling system to determine the exact location of all the fobs.
To maintain the correct level of security when performing certain passive entry related functions such as lock, unlock, etc., it may be necessary to know, at that exact moment, the exact position of the present fobs to determine if the function can be allowed to execute. It can be a time consuming communication process to sequentially activate the necessary amount of antennas required to fully locate all present fob's positions. Because of this penalty, activation latency can contribute to an unfavorable user experience.